Metal forming



Nov. 25, 1969 v N 3,479,979

METAL FORMING Filed Nov. 16, 1967 2 Sheets-Sheet 1 IHL By WQW? A HarneyNov. 25, 1969 G. DUNN 3,479,979

METAL FORMING Filed Nov. 16, 1967 I02 Sheets-Sheet 2 IN TOR.

LLOYD U/VN By Altar/my 3,479,979 METAL FORMING Lloyd G. Dunn, LowerBurrell, Pa., assiguor to Aluminum Company of America, Pittsburgh, Pa.,a corporation of Pennsylvania Filed Nov. 16, 1967, Ser. No. 685,241 Int.Cl. B21d 47/00, 13/10 US. Cl. 113121 7 Claims ABSTRACT OF THE DISCLOSUREA method of making a boss in sheet metal by positioning a sheet ofinetal between mating faces of an anvil and a punch, the face of thepunch extending outwardly of the anvil face, and pressing the sheetmetal between the anvil and punch to induce outward flow of the metalthereby forming a boss in the sheet metal.

BACKGROUND OF THE INVENTION The invention to which this applicationpertains relates to forming bosses in sheet metal. Heretofore, bosseshave been formed in sheet metal by various methods. One method is bydrawing the sheet by a single or multiple number of forming steps toachieve the desired boss height. Drawing a hollow boss in sheet metalwill, however, thin the metal over the surface area of the boss and inmany cases the metal is fractured either during the draw or insubsequent metal working operations that may be performed on the boss.This is particularly true when the boss is drawn in a single operation.The metal in the boss fractures because the total surface area of theboss is much greater than the area of the sheet metal from which theboss is formed, the metal of the boss being greatly stretched andthinned.

One method of making a boss in sheet metal other than by drawing is bypartially punching a sector of metal outwardly of the sheet. In thiscase the base of the resulting boss, where it departs from the plane ofthe sheet metal from which it is formed, is very thin. Moveover, theheight of the boss must necessarily be something less than the thicknessof the metal sheet otherwise the sheet metal would be cut through.

Another method of forming a boss in sheet metal is by compressiveforming to cause plastic flow in the sheet metal then reworking theresidually compressed region and displaced metal with different formingtools to produce the boss. The difficulty with this method is that twoforming operations with different tools is necessary. This prior artmethod is shown in United States Patent No. 2,697,953.

My invention overcomes the aforementioned problems and others byproducing in sheet metal a boss of considerable height that'has themetal at its base as thick as the original sheet metal from which it wasformed and the side wall nearly as thick. Moreover, I achieve a bosshaving these desirable structural features in one forming operation.

SUMMARY OF THE INVENTION In accordance with this invention any suitablesheet of metal, such as aluminum, steel, or other ductile metal, isplaced between a first tool, herein referred to as a punch, and a secondtool, herein referred to as an anvil, and pressed therebetween as by animpact blow or squeezing to produce sufiicient permanent deformation ofthe metal to induce outward flow of the metal thereby forming a hollowboss in the sheet metal. The faces of the punch and anvil contacting thesheet metal should mate to such an extent that upon closing to form theboss United States Patent 3,479,979 Patented Nov. 25, 1969 the metalflows uniformly in radial directions. The face of the punch has an areagreater than the area of the face of the anvil and extends outwardly ofthe face of the anvil. The metal being displaced by the pressure appliedby closing of the punch and anvil is prevented from flowing along thepunch sidewall because the face of the punch overhangs or extendsoutwardly of the anvil face and as a result it is displaced in thedirection of the anvil sidewall and forms a hollow boss around theanvil. The increased sheet metal area necessary to make the boss isobtained largely by thinning the area of the sheet metal initiallyoverlying the face of the anvil. The height of the boss may becontrolled by the amount the overlying area of the sheet metal isthinned. Of course, the higher the resistance to deformation of thesheet metal from which the boss is formed the more pressure required todeform the metal to induce the outward flow of metal. Surprisingly, thingage metal such as aluminum in a hard roll temper or container-gradesteel works quite well.

It is an object of this invention to provide a method of forming a bossin sheet metal in a single forming operation.

It is another object of this invention to provide a method of forming aboss having high structural strength in a sheet of ductile metal.

It is another object of this invention to provide a method of forming astructurally strong boss in a sheet of ductile metal by having the baseportion as thick as the parent sheet metal it was made from and the sidewall nearly as thick with the top of the boss the only areasubstantially thinner than the parent sheet metal.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is an enlarged sectional viewshowing the sheet metal positioned between the punch and anvil;

FIGURE 2 is a view similar to FIGURE 1 showing the punch and anvil inclosed position with the boss formed in the sheet metal;

FIGURE 3 is a perspective view of a metal sheet having a boss formedtherein utilizing the invention;

FIGURE 4 is an enlarged sectional view showing one way to reform a bossmade by the invention so that the boss is better adapted for heading tomake an integral hollow headed rivet.

FIGURE 5 is an enlarged sectional view showing heading the reformed bossshown in FIGURE 4; and

FIGURE 6 is a section view showing utilization of a boss made by theinvention to make honeycomb laminated sheet.

DESCRIPTION OF THE EXEMPLARY METHOD Referring to FIGURES 1 and 2 themethod of forming a boss in metal sheet according to my invention issequentially shown. The metal sheet 1 is positioned between a lower die2 having an upstanding anvil 3 and a punch 4. The anvil 3 has a sidewall 3a and a face 312. The punch 4 is an axial alignment with the anvil3 and has a face 5 which has an area greater than and extends outwardlyof the area of the face 3b of the anvil 3. As shown in FIGURE 2, thepunch 4 in cooperation with the anvil 3 upon closing applies asufficient amount of pressure to the metal sheet 1 to induce outward orradial flow of the metal in the metal sheet 1. Either the punch 4 or theanvil 3 or both may be moved relative to each other to apply thenecessary pressure to the metal sheet 1. The metal caused to flow by theap lied pressure cannot move along the side wall of the punch 4 becausethe outwardly extending face 5 prevents it, and as a consequence metalis displaced in the direction of the side wall 3a of anvil 3, therebyforming a boss 6 around the anvil.

The face 5 of the punch 4 and face 3b of the anvil 3 mate one with theother. Preferably the faces of the punch 4 and anvil 3 are substantiallyflat as the mating of fiat faces is more easily accomplished when thetools are made initially and are more easily maintained in a matingcondition during successive boss forming operations.

Although the anvil may be of various shapes, a right cylinder shapedanvil with a fiat face 3b as shown in FIGURES l and 2 is preferredbecause the desirable uniformity of metal flow radially outward inducedby the pressure on the metal sheet by closing the punch and anvil isreadily accomplished.

The anvil 3 may be of any height, however, I have found that control ofthe height of the boss may be more easily accomplished when the anvilheight is equal to the desired height of the boss. The height of theboss may be varied depending upon the height desired for the ultimateuse to which the boss will be put. The diameter of the anvil face 3bshould be equal to the desired top inside diameter of the finished boss.

It can readily be seen in FIGURE 2 that the boss 6 has a thinnedtransverse end wall 7 as a result of the thinning of the metal duringthe forming operation. The metal displaced in forming the thinned endwall 7 provides the additional boss area necessary to obtain a boss ofsuitable height and forms a side wall 8 of appreciably greater sectionthickness than that of the transverse end wall 7. In fact, the side wallthickness throughout the major height of the boss 6 is almost equal tothe original metal sheet thickness, and the section thickness of themetal in the base 18 of the boss 6 remains unaffected. It should benoted that my method of boss forming is preferably accomplished by coldworking but is not limited to such working.

FIGURE 3 shows in perspective the structural characteristics of a boss 6formed in sheet metal 1 in accordance with my invention described aboveand shown in FIG- URES l and 2. With the anvil 3 having a right cylindershape a truncated cone shaped boss is formed.

Bosses formed by my invention may be employed for various purposes. Twosuch uses for the boss will be hereinafter described. FIGURES 4 anddemonstrate the utility of my boss in the formation of a headed rivet toattach a sheet-like element to the metal sheet. ,Specifically such aboss may be employed in the formation of integral rivets useful inattaching opening tabs to easy opening containers designed to be openedmanually without the 'use of a special opening tool. As shown in FIGURE4 reforming die 9 which has a cylindrical recess 10 of the diameterdesired for the reforming boss 6 is closed in cooperation with the lowerdie having an upstanding mandrel 21. By this reforming operation theside wall 8 and base 18 of the boss 6 are moved laterally inward towardthe side wall 23 of the mandrel 21. If desired, the reformed boss may bemade higher by reforming over a mandrel having a height greater than theinside height of the boss 6. In the case of making integral rivets ineasy opening containers there is normally a score line defining thedesired tear-out panel configuration. Although such scoring may, ifdesired, be performed in a separate operation it would be advantageousto simultaneously score the metal sheet as the boss 6 is being reformed.FIGURE 4 shows a scoring rib 11 at the base of the reforming die 9 forthis purpose. When the reforming die 9 in cooperation with the lower die20 is closed to reform the boss 6 the desired scoring Will be impressedinto the metal sheet 1.

After the boss reforming operation is completed as shown in FIGURE 4 anopening tab 13 is placed over the reformed boss. FIGURE 5 shows thecompleted rivet forming operation wherein the reformed boss is headedto' attach an opening tab 13 to the metal sheet 1. A heading punch 14applies pressure to the transverse end wall 7 of the reformed boss toinduce outward flow of the metal in the end wall 7, When the metal ofthe end wall 7 is caused to be displaced by the applied pressure beyondthe peripheral edge 22 of the mandrel 21, the peripheral wall isreversely folded to form a peripheral bead 15 securing the opening tab13 to the metal sheet 1. During this operation the mandrel portion 21 ofthe lower die 20 supports the interior of the reformed boss to preventinward collapse of the reformed boss during the heading operation. Whenthe boss of my invention is to be used for attaching an opening tab tothe metal sheet the mandrel 21 should be sufficiently high to permit themetal to reversely fold to form the peripheral head 15. Ordinarily theheight of the mandrel 21 will be at least the total original thicknessof the sheet metal and the opening tab. The lower die 20 assists inreversely folding the metal to form the peripheral head 15 by supportingthe metal of the sheet in the vicinity of the base of the boss duringthe rivet forming operation.

The sequence of steps shown in FIGURES 4 and 5 are merely onerepresentative method of making an integral rivet from sheet metal usinga boss formed by my invention. Other methods of making headed integralrivets can utilize the boss made by my method wherein differentsubsequent forming or heading techniques are performed on the boss.

FIGURE 6 shows in cross-section metal sheets which have been joinedtogether to form a honeycomb structure utilizing the boss formed inaccordance with my invention. The middle sheet 1 has a number of bosses6 formed therein. A top metal sheet 16 and a bottom metal sheet 17 areplaced on the transverse end walls 7 of the bosses 6 and when inposition the laminate is brazed in accordance with common brazingpractices to unitize the metal sheets and make a rigid honeycomblaminate structure. Fillets 19 produced by the brazing operation jointhe bosses 6 of sheet 1 to sheets 16 and 17. By employing the bossformations provided by my invention the base and side wall of the bosshave high strength and the transverse end wall 7 which was thinned inthe process of making the boss is strengthened by the fillets 19.

While only two applications of the use of a boss made by my invention.have been illustrated and discussed, the utilization of such a boss isnot limited to these two applications but rather extends to anyapplication that requires or can utilize an upstanding boss of the typeherein described. The description in specific detail of the selectedpractice of the invention will suggest to those skilled in the art,various changes, substitutions and other departures from my disclosurewithin the spirit and scope of the appended claims.

What is claimed is:

1. The method of making a hollow boss in sheet metal comprising,positioning a sheet of metal between mating faces of an anvil and apunch, the face of said punch extending outwardly of the face of saidanvil, and establishing relative closing movement between said anvil andsaid punch to apply a compressive force to the sheet metal between saidmating faces to induce outward flow of the metal thereby forming bymetal displacement a hollow boss in the sheet metal around the anvil.

2. The method of making a hollow boss in sheet metal according to claim1 wherein the mating faces of the anvil and punch are substantiallyflat.

3. The method of making a hollow boss in aluminum sheet comprisingpositioning a sheet of aluminum between mating faces of an anvil and apunch, the face of said punch having a greater area and extendingoutwardly of said anvil face, and establishing relative closing movementbetween said anvil and said punch to apply-sufiicient compressivepressure to the sheet to induce outward flow of the metal and by thedisplacement thereofto form a hollow boss in the sheet around the anvil.

4. The method of making a hollow boss in sheet metal comprisingpositioning a sheet of met-a1 between a right cylinder shaped anvilhaving a substantially flat face and a punch having a face mated withand extending radially outward of the anvil face, and pressing the sheetmetal between said anvil and punch faces to induce uniform outward flowof the metal thereby forming by metal displacement a hollow boss in thesheet metal around the anvil.

5. In the method of joining a sheet-like element to a metal sheet bymeans of an integral hollow headed rivet wherein a hollow boss is formedin the metal sheet, the sheet-like element placed over the hollow bossand the boss headed to join the sheet-like element to the metal sheet,the improvement comprising, forming the upstanding hollow boss bypositioning a sheet of metal between mating faces of an anvil and apunch, the face of said punch extending outwardly of the face of saidanvil, and pressing the sheet metal between said faces to induce outwardflow of the metal thereby forming by metal displacement a hollow boss inthe sheet metal around the anvil.

6. In the method of securing a container opening tab to a portion of asheet metal container member by means of an integral hollow headed rivetwherein a hollow boss is formed in the metal container member, theopening tab placed over the hollow boss and the boss headed to securethe opening tab to the container member, the improvement comprisingforming the hollow boss by positioning the sheet metal container memberbetween mating faces of an anvil and a punch, the face of said punchextending outwardly of the face of said anvil, and pressing the sheetmetal container member between said faces to induce outward flow of themetal thereby forming by metal displacement a hollow boss in the sheetmetal around the anvil.

7. In the method of securing a container opening tab to a portion of acontainer member made of aluminum sheet by means of an integral hollowheaded rivet wherein a hollow boss is formed in said container member,the opening tab placed over the holow boss and the boss headed to securethe opening tab to the container member, the improvement comprisingforming the hollow boss by positioning the aluminum container memberbetween a right cylinder shaped anvil having a substantially flat faceand a punch having a face mated with and extending radially outward ofthe anvil face, and pressing the aluminum container member between saidanvil and punch faces to induce outward flow of the aluminum therebyforming by metal displacement a hollow boss in the aluminum containermember around the anvil.

References Cited UNITED STATES PATENTS 3,404,648 12/1967 Rosbottom113-121 DONALD D. GREFE, Primary Examiner U.S. Cl. X.R.

